A police officer responsible for protecting Government officials has been arrested over alleged leaks to the media about the "plebgate" affair.
The 46-year-old, from the Diplomatic Protection Group, was held at his work place in central London on suspicion of misconduct in public office.
He was arrested over alleged leaks linked to the row which led chief whip Andrew Mitchell to quit his Cabinet post amid a storm of protest over claims that he called officers "plebs".
The man was not present at the time of the dispute between Mr Mitchell and officers on duty outside Downing Street.
Three weeks ago, Metropolitan Police commissioner Sir Bernard Hogan-Howe said a file of evidence on the case could be handed to prosecutors by the end of this month.
Scotland Yard said on Thursday that because of "ongoing developments", no interim report had yet been submitted to the Crown Prosecution Service.
Investigators have taken statements from all 800 officers in the Diplomatic Protection Group (DPG) as part of the inquiry.
Two other men have been arrested so far. A 52-year-old Pc who is also from the DPG was held on suspicion of misconduct in public office and bailed until a date in February. A 23-year-old was arrested on suspicion of intentionally encouraging or assisting the commission of an indictable offence and also released on bail.
Four other constables in the unit, which is responsible for protecting Government officials and diplomats, have been placed on restricted duty over misconduct claims.